1. Field of Invention
The current invention relates generally to apparatus, systems and methods for cooling optical fibers. More particularly, the apparatus, systems and methods relate to using a liquid to cool fibers. Specifically, the apparatus, systems and methods provide for actively flowing a fluid across fibers to cool the fibers.
2. Description of Related Art
Fiber optic lasers generally use very long lengths of fiber as the doped gain medium is often several meters long. Fibers also have very high specific volumes (the ratio of surface area to object volume) which provide large areas available for heat transfer. These two properties allow fiber lasers to have 10 kW or more of optical power. However, the size of optical fibers (diameters often well below 1 mm) lends them to difficulties in implementing thermal management systems that fully exploit the thermal properties of optical fibers. Fiber optic lasers are commonly cooled using a bath technique. The heat flux of the fibers is high enough to cause a local heating effect in the fiber due to the stagnation of water in a bath-type configuration; even with a circulator. The fiber may even get hot enough to boil the water in the region surrounding the fiber. The primary limiting factor in power scaling of high power fiber lasers is the temperature of the outermost polymer cladding as its failure temperature is significantly lower than that of the fiber glass. So, efficient removal of heat without incurring a significant increase in polymer temperature is essential for high power fiber lasers. The fiber-in-spool thermal management scheme often results in fiber temperatures many dozens of degrees (C or F) of temperature difference between the fiber and the working fluid. What is needed is a better way of cooling fiber lasers and fibers in general.